More dodgy numbers

If you don’t get Ian Wingrove’s monthly digest of Cycling Answers from the Mayor of London, then you should.  It is super, super dry, but it is a mine of information.  Ian works for London Assembly Member Jenny Jones, and you can subscribe to the digest by emailing Ian.

In the September digest, in amongst the written answers, I found, whilst looking for something else, this:

Bike thefts (1)

Question No: 2462 / 2012

Darren Johnson

Can you provide a breakdown of bike thefts in London by borough for the calendar years 2007 – 2011?

Written response from the Mayor

 

There are lots of ways to have fun with these numbers.  For example, by giving a daily average: in 2011, on average, 61 bikes were reported stolen every day in London (or giving the number correlated against some other unit of time, as in this BBC ‘report’ from 2007). Another fun thing to do (and this is the stand-by of lazy journalists everywhere) is to re-order the table with the highest number of reported thefts first, i.e. create a top 5 London borough league table of reported bike thefts:

1. City of Westminster, 1764 reported bike thefts in 2011

2. Hackney, 1578 reported bike thefts in 2011

3. Islington, 1471 reported bike thefts in 2011

3. Southwark, 1467 reported bike thefts in 2011

5. Camden, 1413 reported bike thefts in 2011

Thus it could be said that a bike is most at risk of being stolen in Westminster, and least likely to be stolen at Heathrow Airport.

Or you could go with a trend, like this: reported bike thefts up by more than 27% since 2007 (or, if you wanted to make a party political point, you could even say something like ‘bike thefts soar by more than a quarter under Boris’).  In fact, the BBC went one further, and went with London bike thefts rise by a third in five years, leaving out of the headline the word ‘reported’, and also failing to mention that reported bike thefts in 2011 are down from 2009, thus allowing partisans to say that Boris has brought reported bike thefts down.

However, this set of numbers should be treated with extreme caution.  First, the City of London is not included in the set (the reason is that the City of London police are entirely separate to the Met, and thus their numbers are not included).  As the highest numbers are in the inner London boroughs, it is likely that City of London would be in the top half of the league table, if not in the top 5.

Second, the numbers of thefts are also a reflection of the numbers of cyclists, and therefore bikes.  I doubt that many people cycle to, from or through Heathrow, and Hackney has one of the highest modal shares of cycling in the U.K., never mind London.  If you don’t follow what I’m getting at, think about it like this: no bikes would mean no bikes to steal, so more bikes means more opportunity to steal bikes, and also a bigger market for stolen bikes (you all know people who have bought an obviously freshly stolen bike from Sclater Street because ‘my bike got stolen’).

Third, these numbers are for reported thefts of bikes, not the total number of thefts.  Accurate numbers for bike thefts are notoriously hard to come by, because of under-reporting.  Estimates of under-reporting of bike thefts vary widely.

Bikeoff quotes 2 different numbers, one from the International Crime Victims survey, which says that 56% of bike thefts are not reported, and the British Crime Survey, which gives a figure of 75% (these are numbers from 2006/7). The US National Crime Victims Survey 2006 has a similar number to the BCS, but an article in a 1996 edition of Transportation Alternatives magazine gives a number of 90%!

So the upward (or downward) trend could merely be that more victims of bike theft are reporting their loss to the police, or (as someone suggested on Twitter) the upward trend could be a reflection of higher rates of cycling in London.  There are serious doubts as to whether more people were cycling further in London in 2011 than in 2007.  Cycling is reportedly up 81% since 2000, but there are some indications are that the same people are cycling further, not that a lot more people have started cycling.

According to this UK Bike Biz article, sales of new bicycles in the UK actually declined slightly from 2010 to 2011, so it’s perfectly possible that there were less shiny new bikes in London, which could mean all sorts of things, for instance, less shiny new bikes,  less stolen shiny new bikes, more grubby old stolen bikes, lower prices for stolen bikes, therefore more stealing to make up the drop in income.

So, in other words, Boris 0 – Bike Thieves 22547? Not exactly.